He captured gold for China in the 20-kilometre walk at the London Olympics on Saturday by 11 seconds — enough of a cushion that he could slap the hands of the fans watching the final length of the race.
"By the last lap, I saw I was so far away from everybody that I knew I could win," Chen said.
He raised his arms in joy at the final turn, in front of Buckingham Palace, before focusing on the last meters of the race. Competitors in the walk can be disqualified if both their feet appear to be off the ground at the same time.
Chen took the lead for good at the 18-kilometre mark and finished in 1 hour, 18 minutes, 45 seconds. The gold medal came a day before his 20th birthday.
"I did not do so well in school and wanted to do sports so I don't have to go school," he said. "I was interested in running, but I ended up in walking because they came to my school and told me to try. And here I am."
Erick Barrondo of Guatemala got the silver, the first medal of any colour at any games for that country. He said he hoped it would inspire people in his violence-ridden home country.
"It is a country that has suffered much, but that also has dreams," he said. "If somebody tomorrow changes a gun or a knife for a pair of shoes and begins to train for a sport, I would be the happiest person on earth."
Barrondo, who bought a TV for the family so they could watch him compete in the Olympics, called the medal "the greatest blessing that life has given me."
Wang Zhen of China claimed bronze, finishing 39 seconds behind the winner.
Defending champion Valeriy Borchin of Russia collapsed after the 19-kilometre mark, near Buckingham Palace and within sight of the finish line. He was taken on a stretcher to a hospital in the Olympic Park.
Borchin won gold at the world championships in South Korea last year. Russian teammate Vladimir Kanaykin, who was took silver at the worlds, was disqualified on a technical violation with two kilometres to go.